Handheld robot for orthopedic surgery and control method thereof

ABSTRACT

The present invention provides a handheld robot for orthopedic surgery and a control method thereof. The handheld robot of the present invention includes a main body, a grip, a kinematic mechanism, a tool connector, a tool, a force sensor and a positioning unit. The handheld robot of the present invention combines the position/orientation information of the tool acquired by the positioning unit with the force/torque information acquired by the force sensor, and utilizes the combined information to adjust the position of the tool so as to keep the tool within the range/path of a predetermined operation plan. In this way, the precision of the orthopedic surgery can be enhanced, and the error occurred during the surgery can be minimized.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of Taiwanese patent application No.102149096, filed on Dec. 30, 2013, which is incorporated herewith byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a surgical robot, and moreparticularly, to a handheld robot for orthopedic surgery and the controlmethod thereof. The handheld robot of the present invention is able tocombine the position/orientation information of a tool acquired by apositioning unit with the force/torque information acquired by a forcesensor, and is able to utilize the combined information to compensatethe motion of the handheld robot.

2. The Prior Arts

In the field of orthopedic surgery, surgical jigs, computer aidednavigation program or image-guided robotic arm are commonly used toassist surgeons to position the bones during the operation, such as anosteotomy, or surgeries that requires the surgeon to place plant boneplates or bone screws into patients.

In a surgery where surgical jigs are used to help with the measuring andthe positioning of the cut, surgeons often need to switch surgical jigsduring one operation multiple times, which can lead to errors in thepositioning. In addition, the use of a surgical jig also depends onfactors such as the familiarity of the surgeon with the surgical jig,the level of operation technique of the surgeon and clinical experienceof the surgeon. In orthopedic surgeries where computer aided navigationprogram is used for positioning, the navigation program guides thesurgeon to position/orientate the cutting block, so as to mount thecutting block on the bones of the patient. However, in the actualsurgeries, surgeons need to constantly adjust the cutting block manuallyto position/orientate the cutting block as instructed by the navigationprogram, which complicates the positioning process. In recent years,some solutions have been developed addressing the abovementioned issue.For example, an adjusting screw can be used to finely adjust theposition/orientation of the cutting block. However, in the process ofmounting the cutting block with the adjusting screw, the precision ofthe result might still be compromised due to the error occurred duringthe process of fixing the adjusting screw.

In orthopedic surgeries with image-guided robotic arms, medical imagesand robotics are used for the positioning. Before the surgery isperformed, surgeons would acquire computer tomography (CT) image firstso as to prepare the surgery by planning the operation path. During thesurgery, first, the bone of the patient is immobilized, and a positionsystem is used to monitor if the bone is moving. If the bone of thepatient moved during the operation, the positioning system immediatelystarts the re-coordination procedure to ensure the precision and thesafety of the operation. Alternatively, surgeons can utilize thepositioning system to measure the relative position and orientationbetween the bone and the robotic arm, and further perform precisepositioning and bone cutting through dynamic motion compensationcontrol. Herein, the optical positioning system is one of the mostcommonly used positioning systems in the medical industry. The opticalpositioning system utilize an optical tracker to tack thelight-reflecting balls disposed on the bones and the robotic arm,thereby determining information such as the relative position, relativeorientation and relative speed between the robotic arm and the patient.Subsequently, the image-guided robotic arm use the above informationalong with a control method to determine if the parameters of thepatient and the equipment are compliant with the surgical procedure, andfurther compensate the position and orientation of the tool with regardto the patient. However, due to the response bandwidth of the opticalpositioning system, the reaction speed of the robotic arm is limited,which compromises the precision of the operation. In addition, blockageis a more serious matter which occurs quite often in the opticalpositioning system. When the light-reflecting balls are blocked byobstacles, the optical positioning system cannot provide the relativeposition and orientation between the bones and the robotic arm. Hence,in the situation where only optical positioning system is used to assistwith the motion compensation of the robotic arm, the position of therobotic arm cannot be adjusted in time, which can endanger the safety ofthe patient. Furthermore, compared with the conventional bone cuttingtool, the size of the robotic arm is way too huge, which causesinconveniences for the surgeons, and also limits the applicationthereof.

On the other hand, in the conventional control methods for robotic armsthat utilizes medical images and positioning information to compensatethe motion thereof, in order to prevent the tool from damaging the bloodvessels, nerves or soft tissues of the patient, current control methodssimply turn off the motor when the front end of the tool deviates fromthe predetermined operation range/path. Such control methods lack theability to keep the front end of the tool within the range/path of theoperation plan; therefore, surgeons need to control the movement of therobotic arm manually through out the whole operation process, which canbe very exhausting.

SUMMARY OF THE INVENTION

Based on the above reasons, a primary objective of the present inventionis to provide a handheld robot for orthopedic surgeries. The handheldrobot provided by the present invention is able to combine the relativeposition/orientation information between a tool and a bone acquired by apositioning unit with the force/torque information feedback by the boneacquired by a force sensor, and is able to utilize the combinedinformation to compensate the motion of the handheld robot in a quickand timely manner, so as to keep the tool within the range/path of apredetermined operation plan. As a result, the precision of theorthopedic surgery can be enhanced, and the error occurred during thesurgery can be minimized.

Another objective of the present invention is to provide a toolspecifically designed for further detecting a deviation force betweenthe bone and the tool. With the design of the present invention, thesensitivity of the motion compensation of the tool is improved, therebypreventing the tool from deviating from the path of the predeterminedoperation plan.

For achieving the foregoing objectives, the present invention provides ahandheld robot for orthopedic surgery. The handheld robot includes: amain body, a grip, a kinematic mechanism, a tool connector, a tool, aforce sensor and a positioning unit. The main body has an inner space.The grip is connected at a side of the main body. The kinematicmechanism has six degrees of freedom and is disposed inside the innerspace of the main body. The kinematic mechanism at least includes astationary plate, a mobile plate and a plurality of actuating units. Theactuating units are mounted on the stationary plate and are connectedwith the mobile plate via a plurality of connecting rods. The toolconnector is disposed on the mobile plate. The tool has a threadedsegment and a non-threaded segment, and is connected at the toolconnector. The threaded segment has a first diameter, the non-threadedsegment has a second diameter, and the first diameter is smaller thanthe second diameter. The force sensor is disposed between the toolconnector and the mobile plate. The positioning unit is disposed on themobile plate for positioning the position and orientation of the tool.The force sensor measures a force, which is parallel to an axialdirection of the tool, between an object and the tool, and the forcesensor further measures a deviation force between the tool and theobject in coordination with the difference in the diameters between thethreaded segment and the non-threaded segment. The handheld robot asdescribed combines a position/orientation information acquired by thepositioning unit with the force/deviation force information measured bythe force sensor, and adjusts the position and orientation of the toolbased on a combined information.

According to an embodiment of the present invention, the kinematicmechanism further includes a motor mounting plate mounted on thestationary plate. In addition, each of the actuating unit includes: amotor, a coupling, a lead screw and a slider. The motor is disposed onthe motor mounting plate. The coupling is disposed between the motor andthe motor mounting plate. The lead screw is connected to the motor. Theslider is engaged with the lead screw via a sliding block, wherein anend of the slider is connected with the connecting rod via a joint. Whenthe motor drives the lead screw to rotate, the lead screw also drivesthe slider to slide in a linear direction through the sliding block.

According to an embodiment of the present invention, the positioningunit is a plurality of light-reflecting balls; wherein thelight-reflecting balls positions the position and orientation of thetool in coordination with an optical positioning system. Herein, thepositioning unit can also be other conventional positioning unit, suchas an electro-magnetic positioning system or an inertia measurement unit(IMU).

According to an embodiment of the present invention, the tool connectorincludes a spindle motor for driving the tool to rotate.

According to an embodiment of the present invention, another forcesensor is disposed between the grip and the main body for measuring theforce applied by the user when operating the handheld robot.

In addition, the present invention provides a control method forcontrolling the handheld robot for orthopedic surgery as describedabove. The control method of the present invention includes thefollowing steps: preparing an operation plan with a predeterminedrange/path; acquiring a position/orientation information of a tool,which is disposed at a front end of the handheld robot, with apositioning unit, and adjusting the position/orientation of the toolbased on the position/orientation information acquired, so as to keepthe tool within the predetermined range/path of the operation plan; andmeasuring a force/torque between the tool and an object with a forcesensor, and adjusting the position/orientation of the tool based on themeasured force/torque, so as to keep the tool within the predeterminedrange/path of the operation plan. The force/torque measured by the forcesensor includes a deviation force between the tool and the object.

According to an embodiment of the present invention, the control methodfurther include a step of combining the position/orientation informationacquired by the positioning unit with the force/torque informationmeasured by the force sensor, and adjusting the position/orientation ofthe tool based on a combined information.

According to an embodiment of the present invention, the tool includes athreaded segment and a non-threaded segment. The threaded segment has afirst diameter, the non-threaded segment has a second diameter, and thefirst diameter is smaller than the second diameter.

According to an embodiment of the present invention, when the robot isused for drilling, the deviation force/torque includes a force/torqueorthogonal to an axial direction of the tool. In addition, the methodfurther comprises calculating a drilling force/torque, which is aforce/torque parallel to the axial direction of the tool, to determineif the drilling is completed.

According to an embodiment of the present invention, when the robot isused for cutting, the deviation force/torque includes a force parallelto a normal vector of a cutting surface, and also includes two torquesthat are orthogonal to the normal vector of the cutting surface. Inaddition, the method further comprises calculating a cuttingforce/torque, which are a force parallel to the cutting surface and atorque orthogonal to the cutting surface, to determine if the cutting iscompleted.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be apparent to those skilled in the art byreading the following detailed description of a preferred embodimentthereof, with reference to the attached drawings, in which:

FIG. 1 is a perspective view of a handheld robot for orthopedic surgeryaccording to a preferred embodiment of the present invention;

FIG. 2 is a side view of the handheld robot according to the preferredembodiment of the present invention;

FIG. 3 is an exploded and perspective view of the handheld robotaccording to the preferred embodiment of the present invention;

FIG. 4A and FIG. 4B are enlarged views of a tool according to thepreferred embodiment of the present invention, respectively;

FIG. 5 is schematic view illustrating the handheld robot of the presentinvention being used in a surgery according to the preferred embodiment;

FIG. 6 is a schematic view illustrating the handheld robot of thepresent invention being used for drilling in a bone plate fixationsurgery, wherein the tool offsets from the path of a predeterminedoperation plan;

FIG. 7 is a schematic view illustrating the handheld robot of thepresent invention being used for drilling in the bone plate fixationsurgery, wherein the tool deviates from the path of the predeterminedoperation plan with an angle;

FIG. 8 is a schematic view illustrating the handheld robot of thepresent invention being used for drilling in an intramedullaryinterlocking screw fixation surgery, wherein the tool offsets from thepath of a predetermined operation plan;

FIG. 9 is a schematic view illustrating the handheld robot of thepresent invention being used for drilling in the intramedullaryinterlocking screw fixation surgery, wherein the tool deviates from thepath of the predetermined operation plan with an angle;

FIG. 10 is a flow chart showing a control method of the presentinvention, wherein the position and the orientation of the tool isadjusted based on the position/orientation information acquired by apositioning unit;

FIG. 11 is a flow chart showing the control method of the presentinvention, wherein the position/orientation of the tool is adjustedbased on the force/torque information acquired by a force sensor, andthe handheld robot of the present invention is being used for drillingor tightening bone screws in an operation;

FIG. 12 is a schematic view illustrating the handheld robot of thepresent invention being used in an osteotomy;

FIG. 13 is a schematic view illustrating the handheld robot of thepresent invention being used in an osteotomy such as during a totaljoint replacement surgery, wherein the tool cuts beyond the range of apredetermined operation plan;

FIG. 14 is a schematic view illustrating the handheld robot of thepresent invention being used in the osteotomy such as during a totaljoint replacement surgery, wherein the tool cuts beyond the range of thepredetermined operation plan;

FIG. 15 is a flow chart showing the control method of the presentinvention, wherein the position/orientation of the tool is adjustedbased on the force/torque information measured by the force sensor, andthe handheld robot of the present invention is being used in anosteotomy;

FIG. 16 is a schematic view illustrating the handheld robot of thepresent invention being used to fix a cutting block; and

FIG. 17 is a flow chart showing the control method of the presentinvention, wherein the position/orientation of the tool is adjustedbased on the force/torque information measured by the force sensor, andthe handheld robot of the present invention is being used to fix acutting block.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a perspective view showing a handheld robot 100 for orthopedicsurgery of the present invention. As shown in FIG. 1, the handheld robot100 according to a preferred embodiment of the present invention 100includes: a main body 1, a grip 2, a kinematic mechanism 3, a toolconnector, a tool 5, a force sensor and a positioning unit 7.

FIG. 2 is a side view showing the handheld robot 100 according to thepreferred embodiment of the present invention, and FIG. 3 is an explodedand perspective view of the handheld robot 100 according to thepreferred embodiment of the present invention. As shown in FIG. 1˜FIG.3, the main body 1 has an inner space 10, and the grip 2 is connected ata side of the main body 1 for a user to grip on. A button 21 is disposedon the grip 2 for turning on or turning off the handheld robot 100. Thekinematic mechanism 3 has six degrees of freedom, and is disposed insidethe inner space 10 of the main body 1. The kinematic mechanism 3 atleast includes a stationary plate 31, a mobile plate 32 and a pluralityof actuating units 33. The actuating units 33 are mounted on thestationary plate 31, and are connected with the mobile plate 32 via aplurality of connecting rods 34. The structure and actuation method ofthe kinematic mechanism 3 will be described in details in the followingsections.

In the preferred embodiment of the present invention, the kinematicmechanism 3 is a parallel mechanism with six degrees of freedom. Due tothe features of the parallel mechanism, such as high stability instructure, high rigidity, zero accumulative error, small inertia andsmall working space, the parallel mechanism is best suited for surgicalequipments, which require high accuracy and small working space.

As shown in FIG. 2 and FIG. 3, the kinematic mechanism 3 according tothe preferred embodiment of the present invention further includes amotor mounting plate 35. The motor mounting plate 35 is mounted on thestationary plate 31 with a distance therebetween. Each of the actuationunit 33 includes: a motor 331, a coupling 332, a lead screw 333 and aslider 334. The motor 331 is disposed on the motor mounting plate 35.The coupling 332 is disposed between the motor 331 and the motormounting plate 35. The lead screw 33 is connected to the motor 331through the motor mounting plate 35 and the coupling 332. The slider 334is engaged with the lead screw 333 via a sliding block 3341, wherein anend of the slider 334 is connected with the connecting rod 34 via ajoint 36. Herein, the joint 36 has two degrees of freedom. The other endof the connecting rod 34 is connected with the mobile plate 32 through ajoint 37, which has three degrees of freedom. When the motor 331 drivesthe lead screw 333 to rotate, the lead screw 333 also drives the slider334 to slide in a linear direction through the sliding block 3341, andfurther actuates the connecting rod 34. In the preferred embodiment ofthe present invention, there are six actuating units 33 in the kinematicmechanism 3. With the above configuration, when the actuating units 33actuate the connecting rods 34, the mobile plate 32 is driven to move orrotate to different positions/orientations, thereby moving the tool 5 toa desired position/orientation.

As shown in FIG. 2 and FIG. 3, the tool connector 4 is disposed on themobile plate 32, and the tool 5 is connected at the tool connector 4. Inthe handheld robot 100 of the present invention, tool 5 can be replacedwith suitable tools according to the purpose of each operation. Forexample, in an osteotomy, a milling cutter can be used as the tool 5;when tightening bone screws, a screw driver tool can be used as the tool5; and when the handheld robot 100 is used for drilling, a drill bit canbe used as the tool 5. The tool connector 4 includes a spindle motor 41for driving the tool 5 to rotate. The force sensor 6 is disposed betweenthe tool connector 4 and the mobile plate 32 for measuring theforce/torque generated between the tool and the bone during theoperation.

Herein, it is worth mentioning that the tool 5 according to thepreferred embodiment of the present invention has been designedspecifically to enhance the sensitivity of the force sensor 6. FIG. 4Ais an enlarged view showing a front end of a milling tool 5 a accordingto the preferred embodiment of the present invention, and FIG. 4B is anenlarged view showing a front end of a drilling tool 5 b according tothe preferred embodiment of the present invention. As shown in FIG. 4Aand FIG. 4B, the milling tool 5 a and the drilling tool 5 b both includea threaded segment 51 and a non-threaded segment 52. The threadedsegment 51 of the tools has a first diameter, and the non-threadedsegment 52 of the tools has a second diameter. As can be seen in thefigures, the first diameter is smaller than the second diameter, and adiameter difference d′ exists between the threaded segment 51 and thenon-threaded segment 52.

Under the situation where normal tools are used, the force sensor 6 isonly able to measure the force that is directly exerted on the tool bythe bones of the patient; in other words, the force sensor 6 is onlyable to measure the force which is parallel to an axial direction of thetool. However, if the tool offsets or deviates from the path of apredetermined operation plan when the threaded segment drills into thebones, it is more difficult for force sensor to detect the deviationforce exerted on the tool by the bone with conventional tools, that is,it is more difficult to detect the force/torque orthogonal to the axialdirection of the tool. As a result, it is more difficult for the forcesensor 6 to detect the situation in which the tool offsets from the pathof a predetermined operation plan, or the situation in which the tooldeviates from the path of a predetermined operation plan with an angle.With the specially designed tool 5 of the present invention, the bone ofthe patient will collide with the diameter difference d′ between thethreaded segment 51 and the non-threaded segment 52 when the threadedsegment 51 of the tool 5 drills through the bones, and a deviation forceis generated therebetween. In other words, the force sensor 6 woulddetect a force that is orthogonal to the axial direction of the tool 5,or the force sensor 6 would detect a torque generated between the bonesand the tool 5. In this way, the sensitivity of the force sensor 6 canbe enhanced.

As shown in FIG. 2 and FIG. 3, the positioning unit 7 is disposed on themobile plate 32 for positioning the position and orientation of the tool5. The positioning unit 7 can be any conventional positioning systems,such as an optical positioning system, an electro-magnetic positioningsystem or an inertia measurement unit. In the preferred embodiment ofthe present invention, the positioning unit is a plurality oflight-reflecting balls, which can track the position and orientation ofthe tool 5 when used with an optical positioning system. In addition,another force sensor 6 can be disposed between the grip 2 and the mainbody 1 to further measure the force exerted by the hand of the userduring the operation.

FIG. 5 is schematic view illustrating the handheld robot 100 of thepresent invention being used in a surgery according to the preferredembodiment. As shown in FIG. 5, when the handheld robot 100 of thepresent invention is in use, a user holds the handheld robot 100 withhis/her hand and operate on the bones of a patient according to apredetermined operation plan. Because the kinematic mechanism 3 of thehandheld robot 100 is a parallel mechanism, the size of the handheldrobot 100 is smaller compared to conventional mechanical robotic arms,and the agility of the handheld robot 100 is also higher when in use.During an operation, the handheld robot 100 is used in coordination withan optical positioning system 71 to track the positioning unit 7disposed on the mobile plate 32, so as to determine the relativeposition and orientation of the tool 5 with regard to the bones. Inaddition, when the tool 5 comes into contact with the bone of thepatient, the force sensor 6 measures the force and torque between thetool and the bone to further determine the relative position andorientation of the tool 5 with regard to the bone. In this way, thehandheld robot 100 combines the position/orientation information of thetool 5 acquired by the positioning unit 7 with the force/torqueinformation measured by the force sensor 6, and utilizes the combinedinformation to adjust the position of the tool 5 so as to keep the tool5 within the range/path of a predetermined operation plan.

With reference to the figures, cases in which the handheld robot 100 ofthe present invention is used in different operations will be explainedin details in the following section.

FIG. 6 and FIG. 7 are schematic views illustrating the handheld robot100 of the present invention being used for drilling in a bone platefixation surgery; and FIG. 8 and FIG. 9 are schematic views illustratingthe handheld robot 100 of the present invention being used for drillingin an intramedullary interlocking screw fixation surgery. In FIG. 6˜FIG.9, the user uses the handheld robot 100 of the present invention todrill with automatic positioning function. In FIG. 6(a), FIG. 7(a), FIG.8(a) and FIG. 9(a), before the tool 5 is in contact with the bone of thepatient, the position/orientation of the tool 5 is adjusted based on theposition/orientation information acquired by the positioning unit 7.FIG. 10 is a flow chart showing a control method of the presentinvention, wherein the position/orientation of the tool 5 is adjustedwith the assistance of the positioning unit 7 before the tool 5 is incontact with the bone. As shown in FIG. 10, the handheld robot 100calculates the position/orientation of the tool 5 based on apredetermined operation plan, and also based on the relativeposition/orientation information of the tool 5 with regard to the boneacquired by the positioning unit 7. If the position/orientation of thetool 5 needs to be adjusted, the handheld robot 100 adjusts theposition/orientation of the tool 5 through the kinematic mechanism 3, sotool 5 can be aligned with the position/orientation according to thepredetermined operation path, thereby achieving dynamic motioncompensation of the tool.

Once the tool 5 is in contact with the bone and the drilling process isstarted, a force is exerted on the tool 5 by the bone. At this moment,if the bone or the hand of the user moves and causes the tool 5 todeviate from the target position/orientation, the non-threaded segment52, to be more exact, the diameter difference d′ between thenon-threaded segment 52 and the threaded segment 51 will collide withbone plates, bone screws or bones, thereby generating a deviation force.As shown in FIG. 6(b) and FIG. 8(b), when the tool 5 or the bone offsetsfrom the predetermined path in a direction, a reaction force isgenerated between the bone and the tool 5 in a corresponding direction,that is, a force which is orthogonal to the axial direction of the tool5 is generated therebetween. As shown in FIG. 7(b) and FIG. 9(b), whenthe tool 5 deviates from the predetermined path 5 with an angle, atorque is generated between the bone and the tool 5. In the abovesituations, the force sensor detects and measures the force/torque whichcauses the tool 5 to offset/deviate. The handheld robot 100 then adjustthe position/orientation of tool 5 through the kinematic mechanism 3based on the information acquired by the force sensor 6, so as to keepthe tool 5 within the path of the predetermined operation plan, as shownin FIG. 6(c), FIG. 7(c), FIG. 8(c) and FIG. 9(c).

FIG. 11 is a flow chart showing the control method of the presentinvention, wherein the position/orientation of the tool is adjustedbased on the force/torque information acquired by the force sensor 6,and the handheld robot 100 of the present invention is being used fordrilling or tightening bone screws in an operation. As shown in FIG. 11,the handheld robot 100 measures the force/torque between the tool 5 andthe bone with the force sensor 6 to help with the position/orientationcompensation of the tool 5. By calculating the deviation force/torque,the position/orientation of the tool 5 is adjusted to minimize theforce/torque orthogonal to the axial direction of the tool and betweenthe tool 5 and the bone, so as to prevent the tool 5 from deviating oroffsetting from the path of the predetermined operation plan. The forcesensor then measures and calculates the force/torque exerted by the tool5 during the drilling process, that is, the force which is parallel tothe axial direction of the tool 5. The force parallel to the axialdirection of the tool 5 is used as a basis for determining if the tool 5has drilled through the bone, or, as the basis for determining if thebone screw has been completely tightened. If the tool 5 has drilledthrough the bone or if the bone screw has been completely tightened, thehandheld robot 100 then turn off the spindle motor 41, so the tool doesnot damage other tissues.

The force/torque information acquired by the force sensor 6 as describedabove can be further combined with the relative information/orientationinformation of the bone to the tool 5 provided by the positioning unit 7(e.g. using the multirate Kalman filter for data fusion). As a result,the handheld robot 100 of the present invention is able to achievedynamic motion compensation quickly and accurately, thereby keeping tool5 within the path of the predetermined operation plan.

FIG. 12˜FIG. 14 are schematic views showing the handheld robot 100 ofthe present invention being used in an osteotomy. In FIG. 13(a) and FIG.14(a), similar to the situation in which the handheld robot 100 is usedfor drilling, the position/orientation of tool 5 is adjusted based onthe positioning/orientation information provided by the positioning unit7 before the tool 5 contacts the bone; in other words, the controlmethod in FIG. 10 is used before tool 5 contacts the bone of thepatient. Once the cutting begins when the tool 5 contacts the bone, aforce is generation between the tool 5 and the bone. At this moment, ifthe bone or the hand of the user moves and causes the tool 5 to deviatefrom the target position/orientation, the non-threaded segment 52, to bemore exact, the diameter difference d′ between the non-threaded segment52 and the threaded segment 51 will collide with the bone and generate adeviation force. As shown in FIG. 13(b), when the tool 5 or the boneoffsets from the range of the predetermined operation plan in adirection, a reaction force is generated in the corresponding directionbetween the bone and the tool; that is, the reaction force, which isparallel to the normal vector of the cutting surface, is generatedbetween the bone and the tool. As shown in FIG. 14(b), when the tool 5deviates from the range of the predetermined operation plan with anangle, torques are generated between the bone and the tool 5; to be moreexact, two torques, which are orthogonal to the normal vector of thecutting surface, are generated between the bone and the tool 5. Afterthe force sensor 6 measures the deviation force/torque, theposition/orientation of tool 5 is adjusted through the kinematicmechanism, so as to keep tool 5 within the range of the predeterminedoperation plan, as shown in FIG. 13(c) and FIG. 14(c).

FIG. 15 is a flow chart showing the control method of the presentinvention, wherein the position and the orientation of the tool 5 isadjusted based on the force/torque information measured by the forcesensor 6, and the handheld robot 100 of the present invention is beingused in an osteotomy. As shown in FIG. 15, the handheld robot 100 of thepresent invention measures the force/torque between the tool 5 and thebone for the position/orientation compensation of tool 5. By calculatingthe deviation force/torque, the position/orientation of the tool 5 isadjusted to minimize the force parallel to the normal vector of thecutting surface, and also minimize the two toques orthogonal to thenormal vectors of the cutting surface, so as to prevent the tool 5 fromdeviating or offsetting from the range of the predetermined operationplan. In addition, the cutting force measured by the force sensor, inother words, the force parallel to the cutting surface and the torquesorthogonal to the cutting surface are used as the basis for determiningif tool 5 has complete the cutting. Referring to FIG. 12, once the tool5 has passed the dotted line in FIG. 12 and completed cutting, thehandheld robot 100 then turns off the spindle motor 41 to prevent tool 5from damaging other tissues of the patient.

Similarly, the force/torque information acquired by the force sensor 6as described above can be further combined with the relativeinformation/orientation information of the bone with regard to the tool5 provided by the positioning unit 7 (e.g. using the multirate Kalmanfilter for data fusion). As a result, the handheld robot 100 of thepresent invention is able to achieve dynamic motion compensation quicklyand accurately, thereby keeping tool 5 within the range of thepredetermined operation plan.

FIG. 16 is a schematic view illustrating the handheld robot 100 of thepresent invention being used to fix a cutting block 9. First, as shownin FIG. 16(a), the user manually places the cutting block 9 at certainposition/orientation with regard to the bone of the patient as guided bya medical image or computer navigation program. During the process, ifthe position/orientation of the cutting block 9 is slightly off from thedesired position/orientation, the handheld robot 100 of the presentinvention can adjust the position/orientation of the screw driver andthe bone screw 55 at the front thereof through the kinematic mechanism 3based on the relative position/orientation information of the tool 5with regard to the bone, and at the same time guides the fixing hole 91of the cutting block 9 to the desired position/orientation as instructedby the navigation program, as shown in FIG. 16(b). Once the bone screw55 enters the bone, there are two approaches to fix the cutting block 9with the handheld robot 100. The first approach to fix the cutting block9 is to use the control method for drilling as described above. Theposition/orientation of the screw driver is adjusted through kinematicmechanism 3 based on the force/torque information provided by the forcesensor 6 to minimize the force/torque orthogonal to the axial directionof the screw driver. The force/toque measured in the direction parallelto the axial direction of the screw drive can be used as the basis fordetermining if the bone screw 51 has been tightened. Meanwhile, thehandheld robot 100 performs fast and accurate dynamic motioncompensation with the relative position/orientation information of thetool with regard to the bone provided by the positioning unit 7. Oncethe bone screw 51 is tightened as shown in FIG. 16(c), the handheldrobot 100 turns off the spindle motor 41. When taking the secondapproach to fix the cutting block 9, the handheld robot 100 is switchedto a manual mode. In the manual mode, the position/orientation of thescrew driver is no longer adjusted through the kinematic mechanism 3;instead, the user adjusts the position/orientation of the screw drivermanually. In the second approach, the rest of the motion can be easilyfinished manually because the bone screw 51 has already passed throughthe fixing hole 91 of the cutting block 9 and is guided to the correctposition/orientation with regard to the bone.

FIG. 17 is a flow chart showing the control method of the presentinvention, wherein the position/orientation of the tool is adjustedbased on the force/torque information measured by the force sensor 6,and the handheld robot 100 of the present invention is being used to fixthe cutting block 9. As shown in FIG. 17, the handheld robot 100 of thepresent invention measures the force/torque between the tool 5 and thebone to assist with the position/orientation compensation of tool 5. Bycalculating the deviation force/torque, the position/orientation of thetool 5 is adjusted to minimize the force orthogonal to the axialdirection of the screw driver, so as to prevent the tool 5 fromdeviating or offsetting from the path of the predetermined operationplan. The tightening force/torque measured by the force sensor 6, thatis, the force, which is parallel to the axial direction of the screwdriver, is used as the basis for determining if the cutting block 9 hasbeen completely fixed. Once the cutting block 9 is fixed, the handheldrobot 100 then stops the spindle motor 41 to prevent the tool 5 fromdamaging other tissues.

The present invention utilize the spatial information of the tool 5 andthe bone of the patient provided by the positioning unit 7 and theforce/torque information measured by the force sensor 6 for data fusion,thereby improving the reaction speed of the motion compensation of thetool 5. Generally speaking, due to the bandwidth of the opticalpositioning system, certain latency is expected in the reaction to theoptical positioning system. Therefore, if surgical equipment only usesthe spatial information provided by the optical positioning system asthe basis of the motion compensation of the front tool thereof, theerror accumulated between the spatial information acquired and theactual spatial information could be too large. In comparison, thereaction speed of surgical equipment to the force/torque information isfaster; therefore, by utilizing the spatial information in coordinationwith the force/torque information, the reaction speed of the surgicalequipment can be enhanced. By using the control method of the presentinvention to adjust the position/orientation of the tool at the front ofthe surgical equipment, the error between the acquired spatialinformation and the actual spatial information is greatly reduced,thereby improving the precision of the operation. In the mean time, thelatency in using the optical positioning system can be reduced, and theblockage situation, which causes the position of the tool to beunreadable, in using the optical positioning system can also beprevented, thereby improving the safety of the operation.

Although the present invention has been described with reference to thepreferred embodiments thereof, it is apparent to those skilled in theart that a variety of modifications and changes may be made withoutdeparting from the scope of the present invention which is intended tobe defined by the appended claims.

What is claimed is:
 1. A handheld robot for orthopedic surgery,comprising: a main body; a grip, connected to the main body; a kinematicmechanism connected to the main body; a tool connector connected to thekinematic mechanism; a tool connected to the tool connector; and a forcesensor configured to measure a deviation force, a deviation torque, or acombination thereof that deviates the tool from a predetermined range, apredetermined path or a combination thereof, wherein the kinematicmechanism is capable to adjust at least one of the position and theorientation of the tool based on the measured deviation force, themeasured deviation torque, or the combination thereof; and a controllerprogrammed to receive an operation plan with the predetermined range,the predetermined path, or the combination thereof, control the forcesensor to measure the deviation force, the deviation torque, or thecombination thereof and control the kinematic mechanism to adjust atleast one of the position and the orientation of the tool based on themeasured deviation force, the measured deviation torque, or thecombination thereof, so as to keep the tool within the predeterminedrange, the predetermined path, or the combination thereof, of thereceived operation plan.
 2. The handheld robot according to claim 1,further comprising: a positioning unit configured to acquire positioninformation, orientation information, or a combination thereof, of thetool, wherein the kinematic mechanism is capable to adjust at least oneof the position and the orientation of the tool further based on theposition information, the orientation information, or the combinationthereof, of the tool, the positioning unit is a plurality oflight-reflecting balls, the light-reflecting balls position the positionand orientation of the tool in coordination with an optical positioningsystem.
 3. The handheld robot according to claim 1, wherein the toolconnector includes a spindle motor configured to drive the tool torotate.
 4. The handheld robot according to claim 1, wherein another saidforce sensor is disposed between the grip and the main body.
 5. Thehandheld robot according to claim 1, wherein the tool has a threadedsegment and a non-threaded segment.
 6. The handheld robot according toclaim 5, wherein the threaded segment has a first diameter, thenon-threaded segment has a second diameter, and the first diameter issmaller than the second diameter.
 7. The handheld robot according toclaim 1, further comprising: a positioning unit configured to acquireposition information, orientation information, or a combination thereof,of the tool, wherein the kinematic mechanism is capable to adjust atleast one of the position and the orientation of the tool further basedon the position information, the orientation information, or thecombination thereof, of the tool, the positioning unit is anelectro-magnetic positioning system, an inertia measurement unit, or acombination thereof.
 8. The handheld robot according to claim 1, whereinthe controller is programmed to acquire position information,orientation information, or a combination thereof, of the tool, andadjust at least one of the position and the orientation of the toolbased on the acquired position information, the acquired orientationinformation, or the combination thereof, so as to keep the tool withinthe predetermined range, the predetermined path, or the combinationthereof, of the received operation plan.
 9. The handheld robot accordingto claim 8, wherein the controller is programmed to combine the acquiredposition information, the acquired orientation information, or thecombination thereof with the measured deviation force, and adjust atleast one of the position and the orientation of the tool based onresult information of the combining.
 10. The handheld robot according toclaim 1, wherein the handheld robot is configured to drill, thedeviation force, the deviation torque, or the combination thereofincludes a force, a torque, or a combination thereof orthogonal to anaxial direction of the tool.
 11. The handheld robot according to claim10, wherein the controller is programmed to calculate a drilling force,a drilling torque, or a combination thereof which is parallel to anaxial direction of the tool to determine if the drilling is completed.12. The handheld robot according to claim 1, wherein the handheld robotis configured to cut, the deviation force, the deviation torque, or thecombination thereof includes a force parallel to a normal vector of acutting surface and includes two torques that are orthogonal to thenormal vector of the cutting surface.
 13. The handheld robot accordingto claim 12, wherein the controller is programmed to calculate acombination of a cutting force and a cutting torque which includes aforce parallel to a cutting surface and a torque orthogonal to thecutting surface to determine if the cutting is completed.